Relationship Between Resistance To Colltotrichum Gloeosporioides And Chemical Components Of Fruit Coat Of Camellia Oleifera Cultivars

Camellia oleifera Abel. is an important edible oil tree species from Southern China.Anthracnose, caused by Colletotrichum gloeosporioides （Penz.）, is responsible for morethan50%of C. oleifera production loss, and C. oleifera varieties differ in their resistanceto anthracnose.1. The aim of this study was to Assess resistance mechanisms bymonitoring physiological and biochemical parameters of differentially resistant cultivarsduring the development of C. oleifera;2. Genetic relationship and diversity amongdifferent disease-resistant Camellia oleifera varieties were analyzed to further distinguishbetween varieties at the molecular level;3. The key bioactive materials which wererelavant with resistance were deterimined and studied by HPLC-DAD-MS. The specificresearch was as follows:1. C. oleifera fruit coats were analyzed between May and September for tannins,anthocyanins. Tannin contents generally declined at the developmental stage （highlyresistant0.50-0.32, medium resistant0.46-0.24, highly susceptible0.48-0.45）, whereas nosignificant difference was found in tannin levels between differentially disease-resistantcultivars （P>0.05）. The growth rate of highly resistant varieties was12.1%higher than ofsusceptible ones in May. On the contrary, the anthocyanin contents of fruit coats in highlyresistant, medium resistant and highly susceptible varieties grew by77.3%,69.4%and51.5%, respectively, and the synthesis rate of anthocyanins changed mildly after August.The anthocyanin contents differed significantly among different cultivars （P <0.01）.2. There was no significant difference in pH levels between the disease-resistantvarieties and the susceptible ones at the developmental stage （P <0.05）. In July, fruit coats insusceptible varieties reached a pH value of5, while resistant varieties had a pH of4-5. Thebuffer capacity of different cultivars generally rose with increasing maturation （highlyresistant6.2-7.43, medium resistant5.33-7.46, highly susceptible5.45-7.12）. In addition, thebuffer capacity of different cultivars increased rapidly from June to August. Buffer capacitydid not differ significantly between different cultivars （P>0.05）.3. PPO, POD and PAL activity in the fruit coats of highly resistant, medium resistantand susceptible strains were determined. The results demonstrate that activity of the three enzymes generally rose with increasing maturity.（1） PPO activity in highly resistant plants increased more rapidly during May-Augustand increased slowly after September, especially in May. PPO activity was18U·g^-1min^-1higher than in highly susceptible plants. PPO activity of medium resistant and highlysusceptible cultivars rose slowly in the first three months, and then declined in August andSeptember. PPO activity of highly susceptible varieties decreased by14U·g^-1min^-1from Julyto September. PPO activity differed significantly between disease-resistant and susceptiblevarieties （P <0.01）.（2） POD activity of disease-resistant varieties was higher than of susceptible ones, andthe increase rate of highly resistant varieties was6.2%higher than in highly susceptiblevarieties in May. POD activities of medium resistant and highly susceptible varietiesdeclined after August by10U·g^-1min^-1and17U·g^-1min^-1, respectively. There wassignificant difference in PPO activity between disease-resistant and susceptible varieties （P=0.0001）.（3） In May, PAL activity of high resistant cultivars was higher than that of mediumresistant and high susceptible by17%and30%, respectively. In July, PAL activity ofsusceptible cultivars declined gradually, whereas that of high resistant and mediumresistant cultivars still increased. PAL activity was significantly different betweendisease-resistant and susceptible cultivars （P=0.0004）.4. Soluble sugar contents of fruit coats gradually increased from the fruitlet period tomaturity period. From May to September, the soluble sugar contents in highly resistant,medium resistant and highly susceptible varieties rose by60.9%,58.6%and40%,respectively. Soluble sugar contents of highly resistant varieties were45%higher than ofhighly susceptible ones. Soluble sugar contents differed significantly betweendisease-resistant and susceptible varieties （P <0.05）.5. The free radical scavenging capacities of fruit coat extracts from highly resistant,medium resistant and highly susceptible varieties of C. oleifera were determined. The resultsdemonstrate that fruit coat extracts with a concentration of2.0mg/mL had strong freeradical-scavenging capacity in different incidence cultivars, and that fruit coat extracts from highly resistant varieties had the highest scavenging capacity with a value of91.46%±0.32%.The free radical scavenging capacity of fruit coat extracts differed significantlybetween different cultivars （P <0.05）.6. Colletotrichum gloeosporioides （anthracnose） is the most destructive disease whichcauses severe economic losses in Camellia spp.. A study was conducted to establish ifgenotypes identified as resistant or susceptible to anthracnose in China could bedistinguished using molecular markers. A total of30unrelated C. spp. genotypes wereselected from three ecotype regions （Huangshan, Shucheng and Fengyang） in Anhuiprovince. Resistant selection was based on disease severity in plants following detachedfruit inoculation. One AFLP selective primer combinations were used to genotype theseaccessions, resulting in147amplified bands. Of these,129（87.76%） informativepolymorphic bands were used for genetic diversity analysis. Genetic similarity coefficientsranged from0.40to0.85among the resistant accessions, indicating high genetic diversityamong them. Cluster analysis grouped the30accessions into two major clusters based onpolymorphic bands. This study provides genetic diversity for future breeding of C. spp. foranthracnose resistance.7. Methanol and mixed solvent of choroform and ethyl acetate extracts from leaves ofC.yuhsiensis Hu of high resistant cultivar, Huizhou-dahong of resistant variety andHuizhou-xiaoqing of susceptible variety were analyzed with HPLC-DAD-MS.C.yuhsiensis leaf was rich in25negative compounds and21positive compounds. Thesecompounds mostly were phenolics, flavonoids, alkaloids, amino acid and someantibacterial properties, e.g. the （2S,3R）-2-amino fourteen carbon-3-alcohol（Xestoaminol C）.30negative compounds in Huizhou-dahong leaf were mostly flavonoidsand phenolic substances. In addition, there were secondary metabolites, e.g. shikimic acid;30positive compounds in Huizhou-dahong leaf were mostly alkaloids, amino acids, andamides etc.18negative compounds in Huizhou-xiaoqing leaf were a few flavonoids andphenolics, e.g. shikimic acid, chlorogenic acid;28positive in Huizhou-xiaoqing leaf weremostly alkaloids and amino acid.